Sorting method with options

First one is, `sort()` by funciton and an ascending option

```pyhon
>>> db.sort(key=lambda item: item['name'], ascending=False)
id    name
1002  Apple
1001  Banana
1004  Berry
1003  Cherry


[4 items, 2 keys]
```

Second one is,

```python
db.sort(by=Order('-name') & Order('id'))
```